in-

CIDE DICTIONARY

in-, prep. [See In, prep. Cf. Em-, En-.].

 A prefix from Eng. prep. in, also from Lat. prep. in, meaning in, into, on, among; as, inbred, inborn, inroad; incline, inject, intrude. In words from the Latin, in- regularly becomes il- before l, ir- before r, and im- before a labial; as, illusion, irruption, imblue, immigrate, impart. In- is sometimes used with an simple intensive force.  [1913 Webster]

in-,  [L. in-; akin to E. un-. See Un-.].

 An inseparable prefix, or particle, meaning not, non-, un- as, inactive, incapable, inapt. In- regularly becomes il- before l, ir- before r, and im- before a labial.  [1913 Webster]

OXFORD DICTIONARY

in-, prefix (also il-, im-, ir-) added to:
1 adjectives, meaning 'not' (inedible; insane).
2 nouns, meaning 'without, lacking' (inaction).

in-, prefix (also il- before l, im- before b, m, p, ir- before r) in, on, into, towards, within (induce; influx; insight; intrude).

Etymology

IN, or from or after L in IN prep.